Security researchers have identified a pop-up address bar spoofing weakness in Microsoft's newly released Internet Explorer 7 browser. The flaw, first reported by security notification firm Secunia, might lend itself to phishing attacks and remains currently unpatched.

The security bug creates a means for hackers to display a popup with partially spoofed address bar where a number of special characters have been appended to a URL. Only part of the address bar will be displayed, creating a possible mechanism to trick users into believing they are visiting a trusted site rather than one controlled by hackers.

The weakness has been confirmed to exist in IE7, running even on a fully patched Windows XP SP2 system. Secunia has constructed a demo designed to illustrate the flaw which can be found here.

A number of possible workarounds have been suggested, pending a fix from Microsoft. Secunia advises surfers not to follow links from untrusted sources. The SANS Institute's Internet Storm Centre suggests a more sophisticated fix involving configuring IE7 to open a new Windows in a new tab, as explained here.

"This vulnerability has a lot of potential for phishers or others that attempt to trick the user into trusting the popup window as they trust the site displayed in the main window," The Internet Storm Centre notes.

Last week, Secunia and Microsoft got into a dispute about whether a separate information disclosure vulnerability affected IE7 or Outlook Express. You can read more on that row in our report here. ®